1. Field of Invention
The present invention relates to a function test device for print head heaters and, in particular, to a function test device for optical print head heaters used in thermal bubble printers.
2. Related Art
The inkjet technology has been widely applied to printers, facsimile machines, and other computer peripheral devices. For thermal bubble inkjet printers, the key element is the thermal bubble inkjet print head.
An inkjet print head is composed of several nozzles, each of which is associated with a heater. When the heater receives an energy pulse, a droplet of ink is pushed out of the print head through the corresponding nozzle. To increase the reliability of printing quality, some basic tests have to be performed on the printer to make sure each energy pulse during a print job is indeed imposed on the heater.
There are many reasons why impulse signals cannot be successfully sent to the heater. Such examples are damaged heaters, broken soft circuit boards, bad contacts between a printer probe and the soft circuit board, and improper installation of the print head. In these cases, a good printer should be able to detect the error. The U.S. Pat. No. 4,996,487 disclosed such a mechanism and method for detecting errors of the heater in an inkjet printer. However, the cited reference can only detect whether the heater is out of order, but cannot test functions of the heater and the isolation property between a test circuit and a printing circuit.
Therefore, it becomes a hot topic to provide a test mechanism and method for testing the functions of an optical heater in a thermal bubble inkjet print head and for forming isolation between a test circuit and a print driving circuit.
An objective of the invention is to provide a device for testing the functions of an optical print head heater in a thermal bubble printer. The device is not only able to detect whether the print head heater is out of order, but can also test the function of the heater. It also provides the isolation between a test circuit and a print circuit.
The disclosed test device contains at least a test end power supply to provide the power needed for the test device; a linear optical coupling device serially connected between a pulse power supply for driving a print head circuit and the print head heater to detect variation of a triggering current; and an amplification circuit to amplify an output signal of the linear optical coupling device and send the signal to a microprocessor.